No abstract

Aim: Since forest planning is characterized by long time horizon and it typically involves large areas of land and numerous stakeholders, uncertainty and risk should play an important role when developing forest management plans. The aim of this study is to review different methods to deal with risk and uncertainty in forest planning, listing problems that forest managers may face during the preparation of management plans and trying to give recommendations in regard to the application of each method according to the problem case. The inclusion of risk and uncertainty in decision support systems is also analyzed.Area: It covers the temporal and spatial scale of forest planning, the spatial context, the participation process, the objectives dimensions and the good and services addressed.Material and methods: Several hundreds of articles dealing with uncertainty and risk were identified regarding different forestry-related topics and approaches. Form them, around 170 articles were further reviewed, categorized and evaluated.Main results: The study presents a thorough review and classification of methods and approaches to consider risk and uncertainty in forest planning. Moreover, new approaches are introduced, showing the opportunities that their application present in forest planning.Research highlights: The study can aid forest managers in the decision making process when designing a forest management plan considering risk and uncertainty.Keywords: operations research; optimal alternative; stochastic risk; endogenous risk; stand level; forest level.

The importance of shrub formations in the Mediterranean area both in terms of area occupied and carbon sequestered by them is currently being recognized. However, due to the lack of suitable models to estimate biomass accumulation and growth rate in this region, the carbon sequestered by these formations is not included when computing the total carbon stocks in aboveground biomass in Mediterranean forest ecosystems, according to the IPCC guidelines. The aim of the present study is to develop equations to predict biomass accumulation and growth rate for the main shrub formations in the region of Andalusia (Southern Spain), using the fraction of canopy cover (FCC m ) and the average height of the shrub formations (H m ) as predictors. To build these models, more than 800 plots were inventoried using destructive sampling; the mean value found in the region for biomass accumulation and annual growth rate being 16.73 Mg ha -1 and 1.14 Mg ha -1 year -1 , respectively. Heathers and big-size Cistaceae formations were the ones that presented the highest values of biomass accumulation (24.99 and 21.01 Mg ha -1 , respectively), while the highest values for annual growth rate were achieved by Leguminous gorse shrubs and, again, bigsize Cistaceae bushes (1.49 and 1.64 Mg ha -1 year -1 , respectively). The carbon content for the main shrub species and formations in the area was also obtained. The developed models provide the opportunity to estimate shrub carbon stocks in Mediterranean forest management from easy-toobtain variables, namely FCC m and H m . Moreover, the used shrub formations classifications and model structure allow their applicability to compute biomass accumulation and growth rate at regional and national level using as input data from the Spanish National Forest Inventory.

Pinus pinaster is the most important conifer in Galicia in terms of volume and production, occurs mainly in plantations. Forest fires are the main threat to forest plantations, affecting optimal stand management. The aim of this study was to develop management prescriptions for P. pinaster based on growth and yield models and optimisations. The objective function was soil expectation value, calculated taking the expected fire losses into account. Fire risk was assumed to consist of two components, probability of occurrence and damage. As the main cause of forest fires in Galicia is arson, the manager cannot significantly influence fire occurrence, which was assumed to be exogenous. Salvage was treated as an endogenous factor depending on the management schedule followed in the stand. Optimisations were done for different initial stands, timber assortments, discount rates and probabilities of fire occurrence. Based on the optimisation results, regression models were developed for the optimal rotation length as well as the timing and intensity of thinnings. The results show that when fire risk is partly endogenous, optimal rotation lengths become shorter with increasing probability of fire occurrence, and optimal thinning becomes heavier and earlier. However, without a price reduction for burned timber, the optimal rotation length increases with increasing probability of fire.

Pinus pinea is one of the most important tree species in the Mediterranean region due to the economic value of its edible seeds called ''piñones''. Timber also represents an important source of income from this species. Generally, P. pinea stands have been managed to maximize either timber or seed production, optimization of the joint production of both products being rare. The difficulty in optimizing seed or joint production is the highly stochastic masting habit of P. pinea. The aim of the present study was to find the optimal management of P. pinea stands from the economic point of view when both seed and timber production are considered. A growth and yield model was employed to simulate the dynamics of P. pinea stands of the northern Iberian Peninsula. The novelty of the study is the implementation of a cone yield model that is able to predict expected cone harvests and seed yields when masting is stochastic. The model was linked with an optimization algorithm to obtain optimal schedules for two different stands. The results showed that seed production of P. pinea in the northern plateau of the Iberian Peninsula may increase the soil expectation value by more than 300 % in dense stands and 200 % in sparse stands. When seed yields were considered, rotation lengths were longer and thinnings were delayed. The results were highly sensitive to cone prices and discount rates.